Aluminum-base alloy



United States Patent ALUMINUM-BASE ALLOY Harold Ernest Gresham, Little Eaton, Alec George Farnsworth, Derby, Douglas W. Hall, Tynemouth, and William Michael Doyle, Slough, England, assignors to Rolls-Royce Limited, Derby, England, a corporation of Great Britain No Drawing. Application October 21, 1953, Serial No. 387,524

Claims priority, application Great Britain October 25, 1952 5 Claims. (Cl. 75-143) This invention relates to an improvement in aluminumbase alloys.

Among the objects of the present invention are to improve the creep and tensile properties of the aluminumbase alloys disclosed in British Patents Nos. 686,819 and 686,820, published January 28, 1953. These British patents disclose two alloys closely resembling one another in composition analysis, one of them (686,819) primarily intended to be used in the forged state after direct chill casting, and the other (686,820) primarily intended to be used in the cast condition.

The aluminum-base alloy which is shown in said British patents, and which is improved in certain properties by the invention hereinafter described, has the following typical approximate composition analysis:

Element:

Copper About 5%. Nickel About 1%. Silicon About 0.15%. Titanium About 0.2%. Manganese About 0.25%. Iron About 0.25%. Antimony (optional) About 0.25%. Cobalt About 0.25%. Balance Essentially aluminum plus impurities.

The permissible ranges for the several constituents, other than residual aluminum, are set forth in detail in the British patents to which reference is hereby made. The following summarizes a portion of the disclosure contained in said patents.

Copper.-Below 4% copper the creep strength athigh temperature (for example, at 300 C.) begins to fall off although it remains good down to about 3.5%. Above 6% copper there is a liability to segregation when the alloy is used in ordinary sand casting but, if the alloy is to be direct chill cast with a view to subsequent forging, the copper is preferably around 6% and can be tolerated up to 7% without serious segregation.

Nickcl.Bclow 0.5% nickel the alloy loses creep strength at elevated temperature. Above 1.5% it tends to become brittle, though if brittleness is comparatively unimportant nickel may be present up to about 2%.

Silicon.-Silicon is a normal impurity to be kept low. In general it is preferred that the silicon should be less than 0.25% and preferably in the approximate range 2,781,262 Patented Feb. 172,

ice

expected to be much below about 0.10%, and in normal foundry practice it can be held to within the approximate range 0.20% to 0.30%. Iron can be tolerated up to 1%, but above that amount there is a tendency to embrittlement and loss of ductility.

Manganese.--Manganese is likewise essential for creep strength. When more than 0.6% is present there is a tendency to embrittlement and segregation.

Antimony.--When the alloy is intended to be used for a casting, antimony should desirably be present in combination with cobalt, mentioned below, in order to achieve good castability and creep strength. Not more than about 0.50% should be present in any event. The preferred amount is less than 0.30%.

C0balt.--This element is essential for creep strength and good castability. If used without antimony, as for example in an alloy to be forged after direct chill casting, the cobalt should not exceed about 0.50%. If antimony and cobalt are both present, as in an alloy intended to be used for a casting, a total of antimony and cobalt togetherexceeding about 0.60% would produce a tendency to segregation, embrittlement.

Reference is made in the above-mentioned British patents to certain other elements which, if present in small quantities, can be tolerated'or may optionally be included for improved qualities of castability or creep strength. One of these is zirconium which, said patents state, may be added up to about 0.4%, provided the total content of zirconium plus titanium does not exceed 0.5%.

According to the present invention a small quantity of cadmium, preferably about 0.10%, is added to the abovedescribed alloy ofthe British patents, either to the form thereof which omits zirconium, or the form thereof which includes zirconium. 1 4

The substantial advantages from the addition of the cadmium begin to appear when about 0.05% thereof has been added. If the percentage of cadmium .exceeds about 0.20% in an alloy intended for forging, the forging material becomes hot-short, that is, tends to become brittle under the forging hammer and to develop cracks. However, where the alloy is to be cast and not forged, cadmium may be added in amounts up to as much as 0.50%.

The addition of cadmium eifects a major increase in the ultimate tensile strength at room temperature of the aluminum-base alloy above referred to, and also a substantial increase in creep strength at temperatures on the order of 200 C. These beneficial effects are achieved without substantially lessening the ultimate tensile strength or the creep strength of the material at higher tempera tures such as 300 C. t t

Example 1 closed in British Patent 686,820 and is of the type in--.

tended for ordinary casting. Alloy B1 is an example of an alloy according to this invention including 'cadimum;

Alloy A1 Alloy B1 Copper 4. 93 4. 96 Nickel. 1.02 0199 Silicon 0. 12 0. 12 Titanium 0. 24 0. 21 Manganese... 0.26 0. 26 Iron 0.31 0. 29 Antimony 0. 23 0. 24 Cobalt. 0. 25 0. 25 Cadmium l 0.09

Balance Balance The following tests were carried out on horizontallycast material which had been solution treated for. 24

menace hours at 530 C., quenched in boiling water and aged for 16 hours at 215 C.

At room temperature, specimens of the above were subjected'to the'0.1% proof tress t st,i. a, the stress in tonsper s in. re uired tQ rodiigeOLiiZ ermanent deformation. For-alloy A1 the stress was 10.4, for alloy B1 it was 17.6, a 'diiference of 69%. I H I At room temperature, the ultimate tensile strength, in tons per -sq. in., of alloy A1 was 17.2,and ofalloy'Bi was 2 0.'1,'a difierence of 16%. b

At 300 C., the 0.1% proof stress in tons per sq. in., after soaking for 1 hour at 300 C., was 5.7 for alloy A1 and 6.8 for alloy B1, a difference of 19%.

Example 2 An alloy'was madeup similar to alloy B1 abovebut containing zirconium, and was found to have thecompositionanalysis' set forth below under the heading alloy C 1, which is an example of an alloy made according to this invention.

I r K 7 Alloy C1 91 1 9 Nic'ke1 1.03 Silicon 0.10 Titanium 0.24 Manganese 0.23 Iron 0.23 Antimony 0.26 Cobalt 0.24 Cadmium 0.09 Zirconium 1 .09 Aluminium Balance At room temperature the 0.1% proof stress in tons per sq. in., for alloy A1 was 10.4 and for alloy C1 was 16.3, a difie'rence of about 56%, and the ultimate tensile strength in tons per sq. in. for alloy A1 was 17.2 and for alloy C1 was 19.4, a difference of about 12%.

At '3'00 C. the 0.1% proof stress, in tons per sq. in., after soaking at 300 C. for one hour, was 5.7 for alloy A and 6.7 for alloy C1, a difference of about 17%, and after'soaking for 400 hours was 5.25 for alloy A1 and 6.45 for alloy C1, a diiference of about 22%. 7

At 300 C. the ultimate tensile strength, in tons per sq. in;,- after soaking at 300 C. for one hour was. 8.1 for allo'y Ai and 8.4 'for alloy C1, a difier'ence ojfabout 3.5%; and after soaking at 300. C. for 400 houifslwas 8.15 for alloy A1 and 9.1 for alloy C1, a difference of about 11%.

' Example 3 Two alloys were made up and heat treated as inExample 1. The composition analyses showed the following:

Alloy m Alloy B,

Copper 4. 07' 4. Nick's 1.06 0. Sillcom- 0. 12 0. Titanium 0.17 0. Manganese :26 0. on 0.24 O. Antimony- 0. 23 0. Cobalt- 0. 25 0. Cadmium". 0 0. Aluminum Balance Balance the'sttess for alloy A; was 4.5, and for .alloy Bz'was 6.4, a difi'rence of about 42%.

7 Example 4 Specimens were prepared in accordance with" ordinary foundry practice of alloy pieces whose composition analysis was found to be as shown in the table below. Alloy A3 is a typical alloy in accordance with British Patent No. 686,819, primarily intended for forging. It difiers from alloy A1 and alloy A2 of the previous examples chiefly in havingv a larger quantity of copper. Alloy B3 is another example of'an alloy made according to this invention.

Alloy A; Alloy 13;

Copper G. 17 6. 12 Nickel 1. 01 1. 08 Slllcom. 0.13 0.13 Titanium 0. l7 0. 17 Manganes 0. 20 0. 26

on 0.23 0.21 Antimony" 0. 25 0. 26 Cobalt; 0. 26 0. 26 Cadmium 0 0.10 Aluminum Balance Balance The following tests were carried out on material which had been solution treated for 24 hours at 540 C., quenched in water at 70 C., and aged for 16 hours at 215 C.

At room temperature, forged piecesof the above alloys gave the following results: The 0.1% proof stress, in tons per sq. in., for alloy As was 14.2 and foralloy B3 was 19.3, a difference of over 35% At room temperature the ultimate tensile strength, in tons per sq..in., of alloy was 22.6 and of alloy B3 was 25.5, a diiference of about 12%. At 300 C. ,the 0.1% proof .stres'sin tons. per sq. in., after soaking for one hour at 300 C. was 6.8 for alloy A3 and 7.65 for alloy B3, a difference of about 12%.

Example 5 A further example of this invention was prepared in accordance withordinary foundry practice and was found to have the composition analysis shown below for alloy c3, which contains both cadmium and'zircon'ium.

The following tests were carried out on material heat treated as mentioned under Example 4.

7 At room temperature, forged pieces of the above alloy showed a-0.1% proof stress, in tons per sq, in., of 18.1, which is about 27% better than the same figure for alloy A3; and an ultimate tensile strength, in tons per sq. in., of 24.7, which is about 9%-better than the same figure for alloy-As.

At300 C., the 0.1% proof stress, after soaking at this temperature -for 400, hours, was 6.45 for alloy A3 and.6.90 for ialloy C2, a difierence of'about 5%. At 300 C. Ithe stress-to fracture ii1100 hours, intonsper 7 sq. .in., was approximately 5;2lfor alloy A3 and approximately 5.8 foralloy Ca, a difference ofabout 11%.

Reference-herein; to tons means long t'onsof 2240 lbs. each. It is not claimed that the condition of cadmium alone producesanyimportant improvement in creep properties at 300 C., although su'chaddition does soat' 200 C. as. pointed out above. However, the addition of cadmiurn'and zirconium together, as describeiproduces the: above mentioned improvements; at 200 C. and in addition brings about significant enhancement-in these properties at 300 C.

What is claimed is:

1. An aluminum-base alloy of the class which consists by weight of about 5% copper, about 1% nickel, about 0.15% silicon, about 0.2% titanium, about 0.25% manganese, about 0.25% iron, up to about 0.25 antimony, about 0.25 cobalt and the balance essentially aluminium plus impurities, characterized in that the alloy contains by weight about 0.05 to 0.50% of cadmium.

2. An aluminum-base alloy of the class which consists by Weight of about 5% copper, about 1% nickel, about 0.15 silicon, about 0.2% titanium, about 0.25 manganese, about 0.25% iron, up to about 0.25% antimony, about 0.25 cobalt and the balance essentially aluminum plus impurities, characterized in that the alloy also contains by weight about 0.05% to 0.5% of cadmium and up to about 0.4% of zirconium.

3. An aluminum-base alloy of the class which consists by weight of about 5% copper, about 1% nickel, about 0.15% silicon, about 0.2% titanium, about 0.25 manganese, about 0.25% iron, up to about 0.25% antimony, about 0.25% cobalt and the balance essentially aluminium plus impurities, characterized in that the alloy also contains by weight about 0.05% to 0.5 of cadmium and about 0.19% of zirconium.

4. An aluminium-base alloy of the class which consists by weight of about 5% copper, about 1% nickel, about 0.15 silicon, about 0.2% titanium, about 0.25 manganese, about 0.25% iron, up to about 0.25% antimony, about 0.25 cobalt and the balance essentially aluminum plus impurities, characterized in that the alloy also contains by weight about 0.10% of cadmium.

5. An aluminum-base alloy of the class which consists by weight of about 5% copper, about 1% nickel, about 0.15 silicon, about 0.2% titanium, about 0.25 manganese, about 0.25% iron, up to about 0.25% antimony, about 0.25 cobalt and the balance essentially aluminium plus impurities, characterized in that the alloy also contains by weight about 0.10% of cadmium and about 0.19% zicronium.

References Cited in the file of this patent UNITED STATES PATENTS 2,063,942 Nock Dec. 15, 1936 FOREIGN PATENTS 686,819 Great Britain Jan. 28, 1953 686,820 Great Britain Jan. 28, 1953 

1. AN ALUMINUM-BASE ALLOY OF THE CLASS WHICH CONSISTS BY WEIGHT OF ABOUT 5% COPPER, ABOUT 1% NICKEL, ABOUT 0.15% SILICON, ABOUT 0.2% TITANIUM, ABOUT 0.25% MANGANESE, ABOUT 0.25% IRON, UP TO ABOUT 0.25% ANTIMONY, ABOUT 0.25% COBALT AND THE BALANCE ESSENTIALLY ALUMINUM PLUS IMPURITIES, CHARACTERIZED IN THAT THE ALLOY CONTAINS BY WEIGHT ABOUT 0.05% OF CADMIUM. 